Air filters



June 23, 1959 B, KNIGHT 2,891,631

AIR FILTERS Filed Jan 2?, 195a United States Patent AIR FILTERS Basil Edward Knight, Eastcote, Pinner, England, assignor to CAN. Limited, London, England Application January 27, 1958, Serial No. 711,203

2 Claims. (Cl. 183-36) This invention relates to air filters. One particular purpose for which the invention is required is on the testing of liquid fuel injection nozzles. The method of testing consists in passing fuel through a nozzle under pressure, and inspecting the form of the emergent jet or jets. In this way information is obtained as to whether the orifice or any of the orifices includes a deformation or obstruction.

Hitherto it has been customary to discharge the nozzle into a spray-box having at one end a window to which the discharge end of the nozzle is presented, the greater part of the fuel being deposited in the box, and the remainder being discharged to the atmosphere by a current of air which is induced to flow into the box through the window by a fan. This method unavoidably results in some fouling of the atmosphere and surroundings of the air exit, and the object of the present invention is to enable this condition to be obviated or minimised in a simple and convenient manner.

The invention is, however, applicable also to other uses in which it is required to cleanse dust or mist laden air resulting from manufacturing or other operations.

An apparatus in accordance with the invention comprises essentially the combination of a rotary fan, a screen associated 'with the fan, a collecting chamber enclosing the fan and screen, a duct for conveying the contaminated air to the fan, and a return duct having a radial inflow entrance for conveying the cleansed air.

In one example of an apparatus in accordance with the invention for the first above-mentioned purpose and as illustrated by the accompanying diagram, there is provided a box a which is divided internally to form an inflow duct 11 and a return flow duct 0. At one end of the box is provided an open window d. This may be wholly or in part from a sheet of glass or other transparent material having a central hole e for admission of a jet or jets from the nozzle 1 to be tested. A continuation g of the duct b leads to the centre of an outward radial flow fan h driven by an electric motor 1'. The periphery of the fan is enclosed by a fine mesh screen 1' which may rotate with the fan or may be fixed. Also the fan and screen are enclosed by a collecting chamber k.

The duct g is surrounded by a return duct m having an entrance compartment adapted to receive the cleansed air from the collecting chamber k, and such that the cleansed air flows into it in an inward radial direction. Preferably the screen i is extended to surround the entrance of the compartment 0. Further the duct m is connected as shown to the return passage 0 in the box a.

The arrangement is such that fuel discharged from the nozzle is directed through the hole in the window d into the open end of the inner duct b, and an air stream is induced in this duct by the fan h. The fuel-laden air is conveyed by the ducts b, g to the fan and is discharged by the fan through the screen 1. By the action of the screen the fuel drops are caused to coalesce and the collected fuel together with any fuel remaining in suspension is propelled into contact with the inner surface of the collecting chamber k, the fuel thus precipitated being collected in the said chamber and discharged to a drain. The cleansed air is then returned from the casing through the compartment 0, duct m, and duct 0 to the front end of the box, and at this end it re-enters the inner duct b. Any residual spray in the air entering the compartment 0 is removed or reduced by the part of the screen extending over the entrance to this passage.

From the foregoing it will be understood that the air required for carrying the fuel discharged from the nozzle is continually circulated within the box. The air flow in the box may also induce a small air flow from the outer atmosphere through the 'window, the excess air thus induced being returned to the atmosphere through a vent in the casing.

The invention is not, however, restricted to the particular purpose above described, as it may be adapted by appropriate modification of constructional details to other analogous uses. Thus the apparatus may be adapt ed to be mounted in a position adjacent to a machine or other apparatus at which the air is contaminated by a noxious dust or mist, the contaminated air being withdrawn by the action of the fan, and the cleansed air being returned to point of entry or elsewhere.

Having thus described my invention what I claim as new and desire to secure by Letters Patent is:

1. An air filtering apparatus comprising in combination a rotary fan of the kind having an axial inlet and a peripheral outlet, a fine mesh screen surrounding and covering the peripheral outlet of the fan, an air inflow duct connected at one end to the inlet of the fan for conveying thereto air to be cleansed, a collecting chamber enclosing the fan and screen to receive air flowing from the fan through the screen, and an air outflow duct surrounding the air inflow duct and having an entrance end which extends radially outwards and is disposed within the collecting chamber to receive cleansed air therefrom.

2. An air filtering apparatus according to claim 1 and having in combination a box provided at one end with a window, and means dividing the interior of the box into a pair of passages which intercommunicate at the end of the box provided with the window, and which communicate respectively with the ends of the air inflow and outflow ducts remote from the fan.

References Cited in the file of this patent UNITED STATES PATENTS 

